It is well known in the casting arts that introduction of foreign matter into a melt can result in unsafe conditions. Where for example, water comes into contact with molten metal a steam expansion explosion or chemical reaction type explosion may result.
In a conventional wheel and band type continuous casting machine such as that disclosed in U.S. Pat. No. 3,279,000, a continuously moving band cooperates with the peripheral casting groove of a continuously rotating casting wheel to form a mold for the continuous casting of metal bar. During operation of such a casting machine it often happens that foreign material becomes inadvertently attached to the mold side of the band. Additionally, many components of band type casting systems purposely apply materials to the casting band. Examples are disclosed in: U.S. Pat. No. 3,322,184 where soot is applied to the mold surfaces; U.S. Pat. No. 3,575,231 where a heat conducting medium is injected into the solidification gap between the cast product and the mold; U.S. Pat. No. 3,976,119 which applies a fluid coating to the mold surface; and U.S. Pat. No. 4,069,860 which provides ablative material on the surface of the casting band. Where either unwanted materials or unwanted excesses of required materials become attached to the casting band, detriment to the cast product can result. Such results may include cast product surface imperfections as well as inner solidification defects such as inverse segregation.
To avoid these problems, it has been suggested that such materials be continuously cleaned from the surface of the band by a band cleaning system which may apply a cleanser and a rinsing agent to the surface of the band at some point remote from the casting mold. Where the cleanser or rinsing agent used is water or similar to water, it must also be thoroughly removed from the band before the band reaches the melt or explosion may result.
An air wipe such as one similar to that disclosed in U.S. Pat. No. 3,722,077 may be used to dry the casting band. An air wipe forces the water off of the band by directing air under pneumatic pressure against the band. Where pneumatic pressure is decreased or lost, however, the water is not removed from the band and the probability of explosion increases significantly. It is for this reason that the fail safe air wipe was invented.